The present invention concerns a method of producing a lighting or signalling device, in particular for a motor vehicle, and more particularly a method of fixing the lens of such a lighting or signalling device.
There is known, for example from the document FR-A-2 696 528, a headlamp comprising an elliptical reflector, a light source at the first focus of the reflector, an intermediate component made from sheet metal comprising a part in the form of a holder with at the front a lip extending gradially towards the inside, a lens comprising a collar projecting towards the outside resting on the lip of the intermediate component, and a retaining ring mounted on the back lip of the lens under prestressing and on limit stops of the intermediate component in order to press the lens onto the front lip of the intermediate component.
In this headlamp, the lip of the intermediate component gets narrower towards the back towards its free end, is mounted with its internal edge receiving the lens on the collar thereof, is adjacent to the convex part of the lens, and the limit stops for the retaining ring are formed in tongues freely cut out in the lateral wall of the intermediate component, are oriented with their free end towards the reflector, are folded radially towards the inside, and extend at an acute angle towards the flat face of the lens.
Such a design has various drawbacks. First of all, it requires an additional component, the retaining ring, being interposed between the lens and the intermediate component, the retaining ring being put in place before the tongues are folded. This additional component has a non-negligible effect on the cost of the headlamp, as well as on the manufacturing time for this headlamp. Furthermore, if this retaining ring is omitted, the lens is not held in its optimum position with respect to the light source, and the headlamp must be rejected. Finally, during folding of the tongues, the lens is frequently broken, which leads to another source of rejects.
There is also known from the document U.S. Pat. No. 6,086,231 an elliptical headlamp in which the lens is held on the intermediate element by deformation of the circumferential part, radially towards the inside, in order to grip the lip of the lens.
The documents FR-A-2 459 938 and BE-A-508 945 describe parabolic headlamps comprising a reflector and a glass, the glass being held by folding over by thermoforming the lateral wall of a strut or by hot crimping the rim of the reflector against the back lip of the glass.
The application of radial forces, that is to say forces perpendicular to the optical axis of the headlamp, is difficult to control, so that it frequently happens that the lens or the glass breaks or cracks, the reject rate then being relatively high.